System and method for implementing application functionality within a network infrastructure

ABSTRACT

A system and method for implementing functionality within a network on behalf of first and second computers communicating with each other through the network. A front-end computer is provided within the network having an interface for communicating data traffic with the first computer. A back-end computer is also implemented within the network having an interface for communicating data traffic with the second computer. A communication channel couples the front-end computer and the back-end computer. Data traffic is encoded over the communication channel in a first process in the front-end computer. Data traffic is also encoded over the communication channel in a second process in the back-end computer, wherein the first process and the second process implement compatible semantics.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.09/835,876, filed Apr. 16, 2001, which is incorporated by referenceherein in its entirety.

FIELD OF THE INVENTION

The present invention relates, in general, to network information accessand, more particularly, to software, systems and methods forimplementing application-independent functionality within a networkinfrastructure.

RELEVANT BACKGROUND

Increasingly, business data processing systems, entertainment systems,and personal communications systems are implemented by computers acrossnetworks that are interconnected by internetworks (e.g., the Internet).The Internet is rapidly emerging as the preferred system fordistributing and exchanging data. Data exchanges support applicationsincluding electronic commerce, broadcast and multicast messaging,videoconferencing, gaming, and the like.

The Internet is a collection of disparate computers and networks coupledtogether by a web of interconnections using standardized communicationsprotocols. The Internet is characterized by its vast reach as a resultof its wide and increasing availability and easy access protocols.Unfortunately, the heterogeneous nature of the Internet makes itdifficult for the hardware and software that implement the Internet toadd functionality.

The Open System Interconnection (OSI) network model usefully describesnetworked data communication, such as the Internet, as a series oflogical layers or protocol layers. Each layer provides services to thelayer above it, and shields the layer above it from details of lowerlayers. Each layer is configured to communicate with other similar levellayers. In general, computers at network nodes (e.g., clients andservers) implement higher level processes including application layer,presentation layer, and session layer processes. Lower level processes,including network layer, data link layer and physical layer operate toplace data in a form suitable for communication across a rawcommunication channel or physical link. Between the higher and lowerlevel processes is a transport layer that typically executes on amachine at the network node, but is highly dependent on the lower levelprocesses.

While standards exist for these layers, application designers have ahigh level of control and can implement semantics and functionality atthe higher layers with a great deal of latitude. In contrast, lowerlayers are highly standardized. Implementing or modifying functionalityin a lower layer protocol is very difficult as such changes can affectalmost all users of the network. Devices such as routers that aretypically associated with infrastructure operate exclusively at thelower protocol layers making it difficult or impossible to implementfunctionality such as real-time processing, data compression, encryptionand error correction within a network infrastructure.

Although the term “Internet infrastructure” encompasses a variety ofhardware and software mechanisms, the term primarily refers to routers,router software, and physical links between these routers that functionto transport data packets from one network node to another.

Internet infrastructure components such as routers and switches are, bydesign, asynchronous. Also by design, it is difficult to accuratelypredict or control the route a particular packet will take through theInternet. This architecture is intended to make the Internet more robustin the event of failures, and to reduce the cost, complexity andmanagement concerns associated with infrastructure components. As aresult, however, a particular node or machine cannot predict thecapabilities of the downstream mechanisms that it must rely on todeliver a packet to its destination. A sending node cannot expect allmechanisms in the infrastructure to support the functions and/or syntaxnecessary to implement such functions as real time processing, datacompression, encryption, and error correction.

For example, it is difficult if not impossible to conduct synchronous ortime-aware operations over the Internet. Such operations include, forexample, real-time media delivery, access to financial markets,interactive events, and the like. While each IP packet includesinformation about the time it was sent, the time base is not synchronousbetween sender and receiver, making the time indication inaccurate.Packets are buffered at various locations through the Internetinfrastructure, and there is no accurate way to ascertain the actual ageor time of issue of the packet. Hence, critical packets may arrive toolate.

Data compression is a well-known technique to improve the efficiency ofdata transport over a communication link. Typically, data compression isperformed at nodes sending the data and decompression performed at anode receiving the data. Infrastructure components responsible forsending the information between the sending and receiving processes donot analyze whether effective compression has been performed, nor canthe infrastructure implement compression on its own. Where either thesending or receiving process is incapable of effective compression, thedata goes uncompressed. This creates undesirable burden that affects allusers. While modems connecting a user over a phone line often applycompression to that link, there is no analogous function within theInternet infrastructure itself. A need exists for Internetinfrastructure components that compress data between network nodes toimprove transport within the Internet.

Similarly, encryption and other data security techniques are well knowntechniques to ensure only authorized users can read data. Likecompression, however, encryption is typically performed by user-leveland application-level processes. If either sending or receiving processcannot perform compatible encryption, the data must be sent in the clearor by non-network processes. A need exists for Internet infrastructurecomponents that apply encryption or other security processestransparently to users.

As another example, forward error correction (FEC) is a known techniqueto reduced traffic volume, reduce latency, and/or increase data transferspeed over lossy connections. FEC adds redundant information, alsoreferred to as error correction code, to the original message, allowingthe receiver to retrieve the message even if it contains erroneous bits.FEC coding can enhances decoded bit error rate values three order ofmagnitude relative to systems not implementing any FEC techniques. Whenthe error can be detected and corrected at the receiving end, there isless need to resend data. FEC is extensively used in many digitalcommunication systems at some level and in mass storage technology tocompensate for media and storage system errors.

However, FEC is not used within the Internet infrastructure. This stemsin part from the additional complexity, cost and management tasks thatsuch capability would impose on the system hardware and software. FECrequires that the sender and receiver both implement compatible FECprocesses. Hence, most if not all infrastructure components would haveto be replaced or modified to implement FEC in an effective manner.Efforts to implement FEC between sending and receiving nodes areoutlined in IETF RFC 2733. This proposed standard applies to real timetransport protocol (RTP) communications between a client and server.This FEC method affects endpoints to a data transfer, but does notaffect servers and or other infrastructure components located betweenthe endpoints. Hence, a need exists for systems and methods thatimplement FEC within the Internet infrastructure to offer the benefitsof FEC technology seamlessly to network users.

In most cases these types of functionality are implemented in higherlevel processes (e.g., the OSI application layer, presentation layer,session layer and/or transport layer). However this requires thatsending and receiving nodes implement a common syntax. For example, bothsending and receiving nodes must implement complementaryencryption/decryption processes, however once this is ensured, thecommunication will be encrypted through out transport. In practice thereare multiple standards for real-time processing, encryption,compression, and error correction, and one or the other node may beunable to support the protocols of the other nodes. Hence, it isdesirable to implement such functionality is a manner that isindependent of the higher level processes so that otherwise incompatibleor incapable application-level processes can benefit.

In other cases, for example real time processing and error correction,it is desirable to have the functionality implemented within the networkinfrastructure, not only between the nodes. For example, implementingerror correction only between the sending and receiving nodes is only apartial solution, as the infrastructure components that operate at lowernetwork layers (e.g., transport, network, data link and/or physicallayer) cannot read error correction codes inserted at higher networklayers. As another example, traffic prioritization within the networkbenefits from knowledge of when packets were actually sent so that theycan be delivered in time for real-time processes.

A particular need exists in environments that involve multiple usersaccessing a network resource such as a web server. Web servers aretypically implemented with rich functionality and are often extensiblein that the functionality provided can be increased modularly to providegeneral-purpose and special-purpose functions. Examples includeinformation services, broadcast, multicast and videoconference services,as well as most electronic commerce (e-commerce) applications. In theseapplications it is important that functionality provided bynetwork-connected resources be provided in a dependable, timely andefficient manner.

Many e-commerce transactions are abandoned by the user because systemperformance degradations frustrate the purchaser before the transactionis consummated. While a transaction that is abandoned while a customeris merely browsing through a catalog may be tolerable, abandonment whenthe customer is just a few clicks away from a purchase is highlyundesirable. However, existing Internet transport mechanisms and systemsdo not allow the e-commerce site owner any ability to distinguishbetween the “just browsing” and the “about to buy” customers as thisinformation is represented at higher network layers that are notrecognized by the infrastructure components. In fact, the vagaries ofthe Internet may lead to the casual browser receiving a higher qualityof service while the about-to-buy customer becomes frustrated andabandons the transaction.

SUMMARY OF THE INVENTION

Briefly stated, the present invention involves a system for implementingfunctionality within a network on behalf of first and second computerscommunicating with each other through the network. A front-end computeris provided within the network having an interface for communicatingdata traffic with the first computer. A back-end computer is alsoimplemented within the network having an interface for communicatingdata traffic with the second computer. A communication channel couplesthe front-end computer and the back-end computer. Data traffic isencoded over the communication channel in a first process in thefront-end computer. Data traffic is also encoded over the communicationchannel in a second process in the back-end computer, wherein the firstprocess and the second process implement compatible semantics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a general distributed computing environment in whichthe present invention is implemented;

FIG. 2 shows in block-diagram form entity relationships in a system inaccordance with the present invention;

FIG. 3 shows a domain name system used in an implementation of thepresent invention;

FIG. 4 shows front-end components of FIG. 2 in greater detail;

FIG. 5 shows back-end components of FIG. 2 in greater detail;

FIG. 6 illustrates in flow-diagram form processes involved in anexemplary implementation of the present invention;

FIG. 7 shows a conceptual block diagram of particular componentsintroduced in FIG. 2 in greater detail;

FIG. 8 shows exemplary pre-processing processes; and

FIG. 9 illustrates exemplary post-processing processes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present inventions involve improvements to communication channelsimplemented through a public network such as the Internet. Theseimprovements are enabled by using front-end and back-end servers,typically implemented as web servers, that are located within thenetwork. It is difficult to define a clear demarcation point for whatmechanisms are “in the network” in contrast with mechanisms “outside ofthe network”. Typically, devices outside the network, such as clientsand servers, establish a channel through the network with each other.Using the OSI network model referenced above, all of the software andhardware mechanisms below the “network” protocol layer in the OSI modelin the client and server computers can be considered within the network.Similarly processes and mechanisms that operate above the network levelin the client and server can be considered “outside the network”.

Given the terminology framework above, certain features of the presentinvention involve implementing processes that provide higher-layerservices within the network. For example, services typically associatedwith the “presentation layer” or “application layer” such as compressionand encryption are implemented within the network. In accordance withthe present invention, these higher-layer processes are implementedbetween machines within the network in a manner that is preferablytransparent to the computers outside the network. In this manner, solong as a common semantic is defined for a pair or set of machineswithin the network, it is not necessary to modify clients, servers, orother infrastructure components such as routers to recognize thesemantic used to provide these higher-layer functions.

A first set of inventions relate to the improved functionality andmetrics available when cooperating front-end and back-end servers areused to transport data through the public network. This first class ofinventions enable an enhanced communication channel in which both endscan be synchronized and so easily know when the other end performedspecific operations such as datagram generation and transmission. Thisenables each side to take actions based on the knowledge that waspreviously only available to the transmitting side. Other functionalityincludes compression of traffic between front-end and back-end usingpublic or proprietary compression mechanisms that can be readilyselected and optimized for the particular content data currently beingtransported. Similarly, encryption/decryption mechanisms can be employedbetween the front-end and back-end for enhanced security withoutimpacting either a web server or a web client that are principles of thetransaction. Forward error correction can be used to reduce the quantityof traffic, improve latency, and/or increase speed of the transportbetween front-end and back-end components.

A second set of inventions relates to performance and functionalityimprovements enabled by implementing the front-end and back-endcomputers as dynamically re-configurable elements. This second class ofinventions enables multiple front-ends to connect with and servicemultiple back-ends and/or one or more web servers or web sites. Theseinventions also include the ability for one front-end to servicemultiple back-ends and by extension multiple web servers or web sites.Similarly, one front-end can service multiple web servers or contentproviders directly.

In one aspect, the present invention involves a system for multiplexingdata from a plurality of links or channels onto a shared bandwidthchannel. The plurality of links may be fixed-bandwidth links, or maythemselves be shared bandwidth links. The plurality of links maycomprise a homogenous user-level protocol, such as HTTP, or may comprisea variety of user level protocols such as HTTP, FTP, NNTP, SMTP and thelike. The plurality of links may similarly comprise homogenousnetwork-layer and/or physical layer protocols, or may comprise a variedset of network-layer and physical layer protocols.

The shared bandwidth channel allows a variety of services to beprovided. Some advantages are achieved simply by multiplexing multiplelinks onto a single channel. This combination enables the single channelto be persistent thereby avoiding overhead associated with setting up,maintaining and breaking down connections that would otherwise berequired of each the multiple links. The single shared channel can alsoinclude more information than the protocols of the plurality of linksallow such as time synchronization information and quality of serviceinformation.

In a particular embodiment, the shared bandwidth channel transportspackets that are composed by selecting data from the plurality of linksin an order and rate determined to provide differential levels ofservice between packets. The differential service levels may mean thatsome of the data are transported with lower latency and/or higherquality of service than other data. The criteria for providingdifferential levels of service are not limited, but in particularembodiments are based on content type, user identity, user history, andsession statistics.

The present invention is illustrated and described in terms of adistributed computing environment such as an enterprise computing systemusing public communication channels such as the Internet. However, animportant feature of the present invention is that it is readily scaledupwardly and downwardly to meet the needs of a particular application.Accordingly, unless specified to the contrary, the present invention isapplicable to significantly larger, more complex network environments,including wireless network environments, as well as small networkenvironments such as conventional LAN systems.

The present invention is particularly useful in applications where thereis a large amount of data communicated between web servers and webclients (i.e., browser software) or where timeliness (e.g., low latencytransport) is important. For example, real-time stock quotes,multi-player games, multi-tiered service to ASP (application serviceprovider) software distribution models benefit from the improvementsprovided by the present invention. Although the present invention willbe described in terms of particular applications, these examples areprovided to enhance understanding and are not a limitation of theessential teachings of the present invention.

For purposes of this document, a web server is a computer running serversoftware coupled to the World Wide Web (i.e., “the web”) that deliversor serves web pages. The web server has a unique IP address and acceptsconnections in order to service requests by sending back responses. Aweb server differs from a proxy server or a gateway server in that a webserver has resident a set of resources (i.e., software programs, datastorage capacity, and/or hardware) that enable it to execute programs toprovide an extensible range of functionality such as generating webpages, accessing remote network resources, analyzing contents ofpackets, reformatting request/response traffic and the like using theresident resources. In contrast, a proxy simply forwardsrequest/response traffic on behalf of a client to resources that resideelsewhere, or obtains resources from a local cache if implemented. A webserver in accordance with the present invention may reference externalresources of the same or different type as the services requested by auser, and reformat and augment what is provided by the externalresources in its response to the user. Commercially available web serversoftware includes Microsoft Internet Information Server (IIS), NetscapeNetsite, Apache, among others. Alternatively, a web site may beimplemented with custom or semi-custom software that supports HTTPtraffic.

FIG. 1 shows an exemplary computing environment 100 in which the presentinvention may be implemented. Environment 100 includes a plurality oflocal networks such as Ethernet network 102, FDDI network 103 and TokenRing network 104. Essentially, a number of computing devices and groupsof devices are interconnected through a network 101. For example, localnetworks 102, 103 and 104 are each coupled to network 101 throughrouters 109. LANs 102, 103 and 104 may be implemented using anyavailable topology and may implement one or more server technologiesincluding, for example UNIX, Novell, or Windows NT networks, orpeer-to-peer type network. Each network will include distributed storageimplemented in each device and typically includes some mass storagedevice coupled to or managed by a server computer. Network 101comprises, for example, a public network such as the Internet or anothernetwork mechanism such as a fibre channel fabric or conventional WANtechnologies.

Local networks 102, 103 and 104 include one or more network appliances107. One or more network appliances 107 may be configured as anapplication and/or file server. Each local network 102, 103 and 104 mayinclude a number of shared devices (not shown) such as printers, fileservers, mass storage and the like. Similarly, devices 111 may be sharedthrough network 101 to provide application and file services, directoryservices, printing, storage, and the like. Routers 109 provide aphysical connection between the various devices through network 101.Routers 109 may implement desired access and security protocols tomanage access through network 101.

Network appliances 107 may also couple to network 101 through publicswitched telephone network 108 using copper or wireless connectiontechnology. In a typical environment, an Internet service provider 106supports a connection to network 101 as well as PSTN 108 connections tonetwork appliances 107.

Network appliances 107 may be implemented as any kind of networkappliance having sufficient computational function to execute softwareneeded to establish and use a connection to network 101. Networkappliances 107 may comprise workstation and personal computer hardwareexecuting commercial operating systems such as Unix variants, MicrosoftWindows, Macintosh OS, and the like. At the same time, some appliances107 comprise portable or handheld devices using wireless connectionsthrough a wireless access provider such as personal digital assistantsand cell phones executing operating system software such as PalmOS,WindowsCE, EPOCOS, and the like. Moreover, the present invention isreadily extended to network devices such as office equipment, vehicles,and personal communicators that make occasional connection throughnetwork 101.

Each of the devices shown in FIG. 1 may include memory, mass storage,and a degree of data processing capability sufficient to manage theirconnection to network 101. The computer program devices in accordancewith the present invention are implemented in the memory of the variousdevices shown in FIG. 1 and enabled by the data processing capability ofthe devices shown in FIG. 1. In addition to local memory and storageassociated with each device, it is often desirable to provide one ormore locations of shared storage such as disk farm (not shown) thatprovides mass storage capacity beyond what an individual device canefficiently use and manage. Selected components of the present inventionmay be stored in or implemented in shared mass storage.

The present invention operates in a manner akin to a private network 200implemented within the Internet infrastructure as shown in FIG. 2.Private network 200 enhances communications between a client 205 and aweb site 210 by implementing any of a variety of processes that enhanceefficiency and/or functionality independently of client 205 and/orserver 210. These processes include time synchronization processes,quality of service management processes, compression processes, securityprocesses, and error correction processes.

In the specific examples herein client 205 comprises a network-enabledgraphical user interface such as a web browser. However, the presentinvention is readily extended to client software other than conventionalweb browser software. Any client application that can access a standardor proprietary user level protocol for network access is a suitableequivalent. Examples include client applications for file transferprotocol (FTP) services, voice over Internet protocol (VoIP) services,network news protocol (NNTP) services, multi-purpose internet mailextensions (MIME) services, post office protocol (POP) services, simplemail transfer protocol (SMTP) services, as well as Telnet services. Inaddition to network protocols, the client application may access anetwork application such as a database management system (DBMS) in whichcase the client application generates query language (e.g., structuredquery language or “SQL”) messages. In wireless appliances, a clientapplication may communicate via a wireless application protocol or thelike.

For convenience, the term “web site” is used interchangeably with “webserver” in the description herein although it should be understood thata web site comprises a collection of content, programs and processesimplemented on one or more web servers. A web site is owned by thecontent provider such as an e-commerce vendor whereas a web serverrefers to set of programs running on one or more machines coupled to anInternet node. The web site 210 may be hosted on the site owner's ownweb server, or hosted on a web server owned by a third party. A webhosting center is an entity that implements one or more web sites on oneor more web servers using shared hardware and software resources acrossthe multiple web sites. In a typical web infrastructure, there are manyweb browsers, each of which has a TCP connection to the web server inwhich a particular web site is implemented. The present invention addstwo components to the infrastructure: a front-end 201 and back-end 203.Front-end 201 and back-end 203 are coupled by a managed datacommunication link 202 that forms, in essence, a private network.

Front-end mechanism 201 serves as an access point for client-sidecommunications. In the process of translating a requested domain nameinto an IP address of a particular server hosting the requested domainname, mechanisms described in reference to FIG. 3 operate to select aparticular front-end mechanism 201. In effect, the domain is dynamicallyassigned to the selected front-end mechanism. More than one front-end201 may host a single domain. So long as a client 205 associates thedomain name with the IP address of the selected front-end 201, allclient requests to the domain will be routed to the selected front-end201.

Front-end mechanism 201 implements a set of processes in the dynamicallyassigned domain that implement a gateway that functions as a substitutefor the web server(s) implementing web site 210 (i.e., from theperspective of client 205, front-end 201 appears to be the web site210). Front-end 201 comprises, for example, a computer that sits “close”to clients 205. By “close”, it is meant that the average latencyassociated with a connection between a client 205 and a front-end 201 isless than the average latency associated with a connection between aclient 205 and a web site 210. Desirably, front-end computers have asfast a connection as possible to the clients 205. For example, thefastest available connection may be implemented in a point of presence(POP) of an Internet service provider (ISP) 106 used by a particularclient 205. However, the placement of the front-ends 201 can limit thenumber of browsers that can use them. Because of this, in someapplications it is more practical to place one front-end computer insuch a way that several POPs can connect to it. Greater distance betweenfront-end 201 and clients 205 may be desirable in some applications asthis distance will allow for selection amongst a greater numberfront-ends 201 and thereby provide significantly different routes to aparticular back-end 203. This may offer benefits when particular routesand/or front-ends become congested or otherwise unavailable.

Transport mechanism 202 is implemented by cooperative actions of thefront-end 201 and back-end 203. Back-end 203 processes and directs datacommunication to and from web site 210. Transport mechanism 202communicates data packets using a proprietary protocol called transportmorphing protocol™ or TMP™. Transport morphing protocol and TMP aretrademarks or registered trademarks of Circadence Corporation in theUnited States and other countries. TMP is implemented over the publicInternet infrastructure in the particular example. Hence, the presentinvention does not require heavy infrastructure investments andautomatically benefits from improvements implemented in the generalpurpose network 101. Unlike the general purpose Internet, front-end 201and back-end 203 are programmably assigned to serve accesses to aparticular web site 210 at any given time.

It is contemplated that any number of front-end and back-end mechanismsmay be implemented cooperatively to support the desired level of servicerequired by the web site owner. The present invention implements amany-to-many mapping of front-ends to back-ends. Because the front-endto back-end mappings can be dynamically changed, a fixed hardwareinfrastructure can be logically reconfigured to map more or fewerfront-ends to more or fewer back-ends and web sites or servers asneeded.

Front-end 201 together with back-end 203 function to reduce trafficacross the TMP link 202 and to improve response time for selectedbrowsers. Traffic across the TMP link 202 is reduced, for example, bycompressing data. Compression can be implemented using any availablecompression mechanism and may operate on a packet-by-packet level or byassembling data from multiple packets to compress across a larger dataset. Although compression may be applied equally to all data, it isknown that some types of data do not benefit from compression. It isalso known that certain compression mechanisms and algorithms are bettersuited for particular types of data. Accordingly, the present inventioncontemplates the dynamic selection of a compression mechanism based onthe type of data being processed. For example, HTML data, which makes upa large proportion of web-based traffic, typically includes ASCII textwhich is known to compress well using, for example, compressed HTMLmechanisms. Encrypted data, however, often does not compress well.Accordingly, the present invention may be implemented to applycompressed HTML techniques to HTML packets while passing encryptedpackets (e.g., packets using a secure HTTP scheme) without attemptingencryption. So long as front-end 201 and back-end 203 share a commonsemantic for performing the compression/decompression processes, anyavailable algorithm may be implemented.

Encryption processes are largely analogous to compression processes inthat they may be implemented by a number of available cipher algorithmsand mechanisms including stream ciphers and block ciphers providingvarious levels of data security. It usually is not valuable to encryptdata that is already encrypted, hence it is contemplated that encryptionmay be selectively applied. Moreover, a vast majority of datatransferred in many applications does not require encryption at all. Theparticular encryption mechanism used by the front-end 201 and back-end203 can be selected based upon the type of data, or designated on afile-by-file basis by a manager of server 210, for example. Front-end201 and back-end 203 must share a common encryption/decryption semantic,however.

In one embodiment, front-end 201 and back-end 203 share operationalinformation such as time synchronization and quality of service metricswith each other. This information is readily communicated by speciallydesignated packets transmitted on TMP link 202, and/or by including aportion of each TMP packet that is used to exchange this operationalinformation. Traffic across link 202 is preferably managed byselectively transmitting packets at a rate determined to provideadequate quality of service and suitable packet delivery time using thisknowledge shared between the front-end 201 and back-end 203. Optionally,this operational information can be shared with processes running onclient 205 and/or server 210 as well, although such sharing wouldrequire special configuration of client 205 and/or server 210 and is notrequired to achieve the benefits of the present invention.

Traffic may be further reduced by using forward error correction (FEC)techniques to compensate for lossy connections. A variety of FECtechniques are known that add various amounts of overhead to thetraffic. The selection of a particular method depends on the quality ofservice (i.e., transit times and packet loss rate and/or bit error rate)of the communication channel being used. In one implementation, astatically defined FEC mechanism can be implemented between front-end201 and back-end 203 based on average or worst-case quality of service(QoS). However, because both front-end 201 and back-end 203 haveknowledge of the QoS metrics of each other and are time synchronized, itis contemplated that the FEC mechanisms can be adaptive to current QoSmetrics. For example, a data packets may be encoded with a 1-bit/byteerror correction code during times of high QoS, and dynamically changedto a 3-bit/byte or 4-bit/byte error correction (or higher) encoding whenQoS degrades. So long as front-end 201 and back-end 203 share a commonsemantic for handling the FEC processes, the actual implementation ofthose processes is very flexible and can be dynamically defined.

The blending of request datagrams results in fewer request:acknowledgepairs across the TMP link 202 as compared to the number required to sendthe packets individually between front-end 201 and back-end 203. Thisaction reduces the overhead associated with transporting a given amountof data, although conventional request:acknowledge traffic is stillperformed on the links coupling the front-end 201 to client 205 andback-end 203 to a web server. Moreover, resend traffic is significantlyreduced further reducing the traffic. Response time is further improvedfor select privileged users and for specially marked resources bydetermining the priority for each HTTP transmission.

In one embodiment, front-end 201 and back-end 203 are closely coupled tothe Internet backbone. This means they have high bandwidth connections,can expect fewer hops, and have more predictable packet transit timethan could be expected from a general-purpose connection. Although it ispreferable to have low latency connections between front-ends 201 andback-ends 203, a particular strength of the present invention is itsability to deal with latency by enabling efficient transport and trafficprioritization. Hence, in other embodiments front-end 201 and/orback-end 203 may be located farther from the Internet backbone andcloser to clients 205 and/or web servers 210. Such an implementationreduces the number of hops required to reach a front-end 201 whileincreasing the number of hops within the TMP link 202 thereby yieldingcontrol over more of the transport path to the management mechanisms ofthe present invention.

Clients 205 no longer conduct all data transactions directly with theweb server 210. Instead, clients 205 conduct some and preferably amajority of transactions with front-ends 201, which simulate thefunctions of web server 210. Client data is then sent, using TMP link202, to the back-end 203 and then to the web server 210. Runningmultiple clients 205 over one large connection provides severaladvantages:

-   -   Since all client data is mixed, each client can be assigned a        priority. Higher priority clients, or clients requesting higher        priority data, can be given preferential access to network        resources so they receive access to the channel sooner while        ensuring low-priority clients receive sufficient service to meet        their needs.    -   The large connection between a front-end 201 and back-end 203        can be permanently maintained, shortening the many TCP/IP        connection sequences normally required for many clients        connecting and disconnecting.    -   Services such as encryption, compression, error correction and        time synchronization that may not be available or efficiently        implemented in particular clients 205 can be practically        implemented in TMP link where the resources required to provide        these services are shared across multiple clients 205.        Using a proprietary protocol allows the use of more effective        techniques to improve data throughput and makes better use of        existing bandwidth during periods when the network is congested.

A particular advantage of the architecture shown in FIG. 2 is that it isreadily scaled. Any number of client machines 205 may be supported. In asimilar manner, a web site owner may choose to implement a site usingmultiple web servers 210 that are co-located or distributed throughoutnetwork 101. To avoid congestion, additional front-ends 201 may beimplemented or assigned to particular web sites. Each front-end 201 isdynamically re-configurable by updating address parameters to serveparticular web sites. Client traffic is dynamically directed toavailable front-ends 201 to provide load balancing. Hence, when qualityof service drops because of a large number of client accesses, anadditional front-end 201 can be assigned to the web site and subsequentclient requests directed to the newly assigned front-end 201 todistribute traffic across a broader base.

In the particular examples, this is implemented by a front-end managercomponent 207 that communicates with multiple front-ends 201 to provideadministrative and configuration information to front-ends 201. Eachfront-end 201 includes data structures for storing the configurationinformation, including information identifying the IP addresses of webservers 210 to which they are currently assigned. Other administrativeand configuration information stored in front-end 201 may includeinformation for prioritizing data from and to particular clients,quality of service information, and the like.

Similarly, additional back-ends 203 can be assigned to a web site tohandle increased traffic. Back-end manager component 209 couples to oneor more back-ends 203 to provide centralized administration andconfiguration service. Back-ends 203 include data structures to holdcurrent configuration state, quality of service information and thelike. In the particular examples front-end manager 207 and back-endmanager 209 serve multiple web sites 210 and so are able to manipulatethe number of front-ends and back-ends assigned to each web site 210 byupdating this configuration information. When the congestion for thesite subsides, the front-end 201 and back-end 203 can be reassigned toother, busier web sites. These and similar modifications are equivalentto the specific examples illustrated herein.

In the case of web-based environments, front-end 201 is implementedusing custom or off-the-shelf web server software. Front-end 201 isreadily extended to support other, non-web-based protocols, however, andmay support multiple protocols for varieties of client traffic.Front-end 201 processes the data traffic it receives, regardless of theprotocol of that traffic, to a form suitable for transport by TMP 202 toa back-end 203. Hence, most of the functionality implemented byfront-end 201 is independent of the protocol or format of the datareceived from a client 205. Hence, although the discussion of theexemplary embodiments herein relates primarily to front-end 201implemented as a web server, it should be noted that, unless specifiedto the contrary, web-based traffic management and protocols are merelyexamples and not a limitation of the present invention.

As shown in FIG. 2, in accordance with the present invention a web siteis implemented using an originating web server 210 operatingcooperatively with the web server of front-end 201. More generally, anynetwork service (e.g., FTP, VoIP, NNTP, MIME, SMTP, Telnet, DBMS) can beimplemented using a combination of an originating server workingcooperatively with a front-end 201 configured to provide a suitableinterface (e.g., FTP , VoIP, NNTP, MIME, SMTP, Telnet, DBMS, WAP) forthe desired service. In contrast to a simple front-end cache or proxysoftware, implementing a server in front-end 201 enables portions of theweb site (or other network service) to actually be implemented in andserved from both locations. The actual web pages or service beingdelivered comprises a composite of the portions generated at eachserver. Significantly, however, the web server in front-end 201 is closeto the browser in a client 205 whereas the originating web server isclose to all resources available at the web hosting center at which website 210 is implemented. In essence the web site 210 is implemented by atiered set of web servers comprising a front-end server 201 standing infront of an originating web server.

This difference enables the web site or other network service to beimplemented so as to take advantage of the unique topological positioneach entity has with respect to the client 205. By way of a particularexample, consider an environment in which the front-end server 201 islocated at the location of an ISP used by a particular set of clients205 and back-end 203 is closely coupled by a private channel to server210. In such an environment, clients 205 can access the front-end server205 without actually traversing the network 101, hence the need forencryption and error correction and time synchronization services arerelaxed with respect to the client-to-front-end link. In such cases theservices provided transparently by enhanced channel 202 aresubstantially a complete substitute for prior services implemented bymodifying client 205 and server 210 themselves.

In order for a client 205 to obtain service from a front-end 201, itmust first be directed to a front-end 201 that can provide the desiredservice. Preferably, client 205 does not need to be aware of thelocation of front-end 201, and initiates all transactions as if it werecontacting the originating server 210. FIG. 3 illustrates a domain nameserver (DNS) redirection mechanism that illustrates how a client 205 isconnected to a front-end 201. The DNS systems is defined in a variety ofInternet Engineering Task Force (IETF) documents such as RFC0883, RFC1034 and RFC 1035 which are incorporated by reference herein. In atypical environment, a client 205 executes a browser 301, TCP/IP stack303, and a resolver 305. For reasons of performance and packaging,browser 301, TCP/IP stack 303 and resolver 305 are often groupedtogether as routines within a single software product.

Browser 301 functions as a graphical user interface to implement userinput/output (I/O) through monitor 311 and associated keyboard, mouse,or other user input device (not shown). Browser 301 is usually used asan interface for web-based applications, but may also be used as aninterface for other applications such as email and network news, as wellas special-purpose applications such as database access, telephony, andthe like. Alternatively, a special-purpose user interface may besubstituted for the more general-purpose browser 301 to handle aparticular application.

TCP/IP stack 303 communicates with browser 301 to convert data betweenformats suitable for browser 301 and IP format suitable for Internettraffic. TCP/IP stack also implements a TCP protocol that managestransmission of packets between client 205 and an Internet serviceprovider (ISP) or equivalent access point. IP protocol requires thateach data packet include, among other things, an IP address identifyinga destination node. In current implementations the IP address comprisesa 32-bit value that identifies a particular Internet node. Non-IPnetworks have similar node addressing mechanisms. To provide a moreuser-friendly addressing system, the Internet implements a system ofdomain name servers that map alpha-numeric domain names to specific IPaddresses. This system enables a name space that is more consistentreference between nodes on the Internet and avoids the need for users toknow network identifiers, addresses, routes and similar information inorder to make a connection.

The domain name service is implemented as a distributed database managedby domain name servers (DNSs) 307 such as DNS_A, DNS_B and DNS_C shownin FIG. 3. Each DNS relies on <domain name:IP> address mapping datastored in master files scattered through the hosts that use the domainsystem. These master files are updated by local system administrators.Master files typically comprise text files that are read by a local nameserver, and hence become available through the name servers 307 to usersof the domain system.

The user programs (e.g., clients 205) access name servers throughstandard programs such as resolver 305. Resolver 305 includes an addressof a DNS 307 that serves as a primary name server. When presented with areference to a domain name (e.g., http://www.circadence.com), resolver305 sends a request to the primary DNS (e.g., DNS_A in FIG. 3). Theprimary DNS 307 returns either the IP address mapped to that domainname, a reference to another DNS 307 which has the mapping information(e.g., DNS_B in FIG. 3), or a partial IP address together with areference to another DNS that has more IP address information. Anynumber of DNS-to-DNS references may be required to completely determinethe IP address mapping.

In this manner, the resolver 305 becomes aware of the IP address mappingwhich is supplied to TCP/IP component 303. Client 205 may cache the IPaddress mapping for future use. TCP/IP component 303 uses the mapping tosupply the correct IP address in packets directed to a particular domainname so that reference to the DNS system need only occur once.

In accordance with the present invention, at least one DNS server 307 isowned and controlled by system components of the present invention. Whena user accesses a network resource (e.g., a web site), browser 301contacts the public DNS system to resolve the requested domain name intoits related IP address in a conventional manner. In a first embodiment,the public DNS performs a conventional DNS resolution directing thebrowser to an originating server 210 and server 210 performs aredirection of the browser to the system owned DNS server (i.e., DNC_Cin FIG. 3). In a second embodiment, domain:address mappings within theDNS system are modified such that resolution of the of the originatingserver's domain automatically return the address of the system-owned DNSserver (DNS_C). Once a browser is redirected to the system-owned DNSserver, it begins a process of further redirecting the browser 301 tothe best available front-end 201.

Unlike a conventional DNS server, however, the system-owned DNS_C inFIG. 3 receives domain:address mapping information from a redirectorcomponent 309. Redirector 309 is in communication with front-end manager207 and back-end manager 209 to obtain information on current front-endand back-end assignments to a particular server 210. A conventional DNSis intended to be updated infrequently by reference to its associatedmaster file. In contrast, the master file associated with DNS_C isdynamically updated by redirector 309 to reflect current assignment offront-end 201 and back-end 203. In operation, a reference to web server210 (e.g., http://www.circadence.com) may result in an IP addressreturned from DNS_C that points to any selected front-end 201 that iscurrently assigned to web site 210. Likewise, web site 210 may identifya currently assigned back-end 203 by direct or indirect reference toDNS_C.

Front-end 201 typically receives information directly from front-endmanager 207 about the address of currently assigned back-ends 203.Similarly, back-end 203 is aware of the address of a front-end 201associated with each data packet. Hence, reference to the domain systemis not required to map a front-end 201 to its appropriate back-end 203.

FIG. 4 illustrates principle functional components of an exemplaryfront-end 201 in greater detail. Primary functions of the front-end 201include translating transmission control protocol (TCP) packets fromclient 205 into TMP packets used in the system in accordance with thepresent invention. It is contemplated that various functions describedin reference to the specific examples may be implemented using a varietyof data structures and programs operating at any location in adistributed network. For example, a front-end 201 may be operated on anetwork appliance 107 or server within a particular network 102, 103, or104 shown in FIG. 1.

TCP component 401 includes devices for implementing physical connectionlayer and Internet protocol (IP) layer functionality. Current IPstandards are described in IETF documents RFC0791, RFC0950, RFC0919,RFC0922, RFC792, RFC1112 that are incorporated by reference herein. Forease of description and understanding, these mechanisms are notdescribed in great detail herein. Where protocols other than TCP/IP areused to couple to a client 205, TCP component 401 is replaced oraugmented with an appropriate network protocol process.

TCP component 401 communicates TCP packets with one or more clients 205.Received packets are coupled to parser 402 where the Internet protocol(or equivalent) information is extracted. TCP is described in IETFRFC0793 which is incorporated herein by reference. Each TCP packetincludes header information that indicates addressing and controlvariables, and a payload portion that holds the user-level data beingtransported by the TCP packet. The user-level data in the payloadportion typically comprises a user-level network protocol datagram.

Parser 402 analyzes the payload portion of the TCP packet. In theexamples herein, HTTP is employed as the user-level protocol because ofits widespread use and the advantage that currently available browsersoftware is able to readily use the HTTP protocol. In this case, parser402 comprises an HTTP parser. More generally, parser 402 can beimplemented as any parser-type logic implemented in hardware or softwarefor interpreting the contents of the payload portion. Parser 402 mayimplement file transfer protocol (FTP), mail protocols such as simplemail transport protocol (SMTP), structured query language (SQL) and thelike. Any user-level protocol, including proprietary protocols, may beimplemented within the present invention using appropriate modificationof parser 402.

To improve performance, front-end 201 optionally includes a cachingmechanism 403. Cache 403 may be implemented as a passive cache thatstores frequently and/or recently accessed web pages or as an activecache that stores network resources that are anticipated to be accessed.In non-web applications, cache 403 may be used to store any form of datarepresenting database contents, files, program code, and otherinformation. Upon receipt of a TCP packet, HTTP parser 402 determines ifthe packet is making a request for data within cache 403. If the requestcan be satisfied from cache 403, the data is supplied directly withoutreference to web server 210 (i.e., a cache hit). Cache 403 implementsany of a range of management functions for maintaining fresh content.For example, cache 403 may invalidate portions of the cached contentafter an expiration period specified with the cached data or by websever 210. Also, cache 403 may proactively update the cache contentseven before a request is received for particularly important orfrequently used data from web server 210. Cache 403 evicts informationusing any desired algorithm such as least recently used, leastfrequently used, first in/first out, or random eviction. When therequested data is not within cache 403, a request is processed to webserver 210, and the returned data may be stored in cache 403.

Several types of packets will cause parser 404 to forward a requesttowards web server 210. For example, a request for data that is notwithin cache 403 (or if optional cache 403 is not implemented) willrequire a reference to web server 210. Some packets will comprise datathat must be supplied to web server 210 (e.g., customer creditinformation, form data and the like). In these instances, HTTP parser402 couples to data blender 404.

In accordance with the present invention, front-end 201 implementssecurity processes, compression processes, encryption processes, errorcorrection processes and the like to condition the received data forimproved transport performance and/or provide additional functionality.These processes may be implemented within pre-processing unit 408, oralternatively implemented within any of the functional components withinfront-end 201. Also, front-end 201 may implement a prioritizationprogram to identify packets that should be given higher priorityservice. A prioritization program requires only that front-end 201include a data structure associating particular clients 205 orparticular TCP packet types or contents with a prioritization value.Based on the prioritization value, parser 402 may selectively implementsuch features as caching, encryption, security, compression, errorcorrection and the like to improve performance and/or functionality. Theprioritization value is provided by the owners of web site 210, forexample, and may be dynamically altered, statically set, or updated fromtime to time to meet the needs of a particular application.

Blender 404 slices and/or coalesces the data portions of the receivedpackets into a more desirable “TMP units” that are sized for transportthrough the TMP mechanism 212. The data portion of TCP packets may rangein size depending on client 205 and any intervening links couplingclient 205 to TCP component 401. Moreover, where compression is applied,the compressed data will vary in size depending on the compressibilityof the data. Data blender 404 receives information from front-endmanager 217 that enables selection of a preferable TMP packet size.Alternatively, a fixed TMP packet size can be set that yields desirableperformance across TMP mechanism 212. Data blender 404 also marks theTMP units so that they can be re-assembled at the receiving end. Datablender 404 may also serve as a buffer for storing packets from allappliances 107 that are associated with front-end 201. In accordancewith the present invention, data blender 404 may associate aprioritization value with each packet.

TMP mechanism implements a TMP protocol, described in greater detailhereinbelow, to communicate TMP packets. Received TMP packets includesubpackets from multiple TCP connections. The data portions ofsubpackets are reassembled by reassemble mechanism 406 into a formsuitable for return to the requesting client 205. For example, in anHTTP environment reassemble mechanism 406 creates HTTP response payloadsakin to what would have been generated by an origin server 210.

Postprocessing mechanism 407 performs decompression, decryption, forwarderror correction and the like on packets received from a back-end 203.As described hereinafter with respect to FIG. 5, back-end 203 preferablyincludes pre-processing mechanisms 508 that are analogous topre-processing mechanisms 408. Hence, post-processing mechanisms 407restore the data to a form usable by a client 205 without additionalprocessing. Accordingly, client 205 need not implement any of thepre-processing or post processing functions while still realizing thebenefits of these processes.

FIG. 5 illustrates principle functional components of an exemplaryback-end 203 in greater detail. Primary functions of the back-end 203include translating transmission control protocol (TCP) packets from webserver 210 into TMP packets as well as translating TMP packets receivedfrom a front-end 201 into the one or more corresponding TCP packets tobe send to server 210. Further, back-end 203 is able to implementsimilar or complementary functionality to that of front-end 203. In thismanner, back-end 203 can operate as a web server to retrieve content andgenerate web pages, analyze and reformat web pages and components withinweb pages, and similar server functionality that would conventionally beimplemented in a server 210. In general, any functionality and behaviordescribed herein that can be implemented on server 210 and/or front-endserver 201 can also be implemented on back-end server 203.

TMP unit 505 receives TMP packets from TMP pipe 212 and passes them toHTTP reassemble unit 507 where they are reassembled into thecorresponding TCP packets. Data filter 506 may implement otherfunctionality such as decompression, decryption, and the like to meetthe needs of a particular application. The reassembled data is forwardedto TCP component 501 for communication with web server 210.

TCP data generated by the web server process are transmitted to TCPcomponent 501 and forwarded to HTTP parse mechanism 502. Parser 502operates in a manner analogous to parser 402 shown in FIG. 5 to extractthe data portion from the received TCP packets. Pre-processing mechanism508 and post-processing mechanism 507 operate in an analogous fashion tocomponents 407 and 408 to perform compression, encryption, errorcorrection, and the like, and forward those packets to data blender 504.Data blender 504 operates in a manner akin to data blender 404 shown inFIG. 5 to buffer and prioritize packets in a manner that is efficientfor TMP transfer. Priority information is received by, for example,back-end manager 209 based upon criteria established by the web siteowner. TMP data is streamed into TMP unit 505 for communication on TMPpipe 212.

In an exemplary implementation, illustrated in FIG. 6 and FIG. 7, a “TMPconnection” comprises a plurality of “TCP connection buffers”, logicallyarranged in multiple “rings”. Each TCP socket 701 maintained between thefront-end 201 and a client 205 corresponds to a TCP connection buffer702. Pre-processing 408 is performed on the TCP connection buffer datato provide, for example, data compression, encryption, and/or errorcorrection coding before the data is placed in the corresponding TCPconnection buffer 702.

When a TCP connection buffer 702 is created, it is assigned a priority.For purposes of the present invention, any algorithm or criteria may beused to assign a priority. Each priority ring is associated with anumber of TCP connection buffers having similar priority. In a specificexample, five priority levels are defined corresponding to five priorityrings. Each priority ring is characterized by the number of connectionbuffers it holds (nSockets), the number of connection buffers it holdsthat have data waiting to be sent (nReady) and the total number of bytesof data in all the connection buffers that it holds (nBytes).

A TCP connection buffer 702 is created and placing one or morepreprocessed packets from a TCP socket 701 within the TCP connectionbuffer 702. A TCP connection buffer 702 is sized to hold a plurality ofTCP packets and each TCP connection buffer 702 is associated with apriority value. The priority value is assigned when TCP connectionbuffer 702 is first created and may be dynamically changed in operation.

When sending data, blender 404 performs a series of processes outlinedin FIG. 6 that access data from the TCP connection buffers 702 to formTMP units 705 that are transmitted. The processes performed by blender404 include:

In step 602, determine the number of bytes available to be sent fromeach ring (nBytes), and the number of TCP connections that are ready tosend (nReady)

In step 603, determine how many bytes should be sent from each ring.This is based on a weight parameter for each priority. The weight can bethought of as the number of bytes that should be sent at each prioritythis time through the loop.

The nSend value computed in the previous step 603 reflects the weightedproportion that each ring will have in a blended TMP packet, but thevalues of nSend do not reflect how many bytes need to be selected toactually empty most or all of the data waiting to be sent a singleround. To do this, the nSend value is normalized to the ring having themost data waiting (e.g., nBytes=nSendNorm) in step 604. This involves acalculation of a factor: S=nBytes/(Weight*nReady) for the ring with thegreatest nReady. Then, for each ring, calculate nReady*S*Weight to getthe normalized value (nSendNorm) for each priority ring.

In step 605, sub-packets are sent from the different rings. This isdone, for example, by taking a sub-packet from the highest priority ringand adding it to a TMP packet, then adding a sub-packet from each of thetop two queues, then the top three, and so on. A variety of algorithmsmay be used to select particular sub-packets from the different rings toimplement a desired level of fairness, prioritization, and quality ofservice.

Referring to step 606, within each ring, sub-packets are added roundrobin. When a sub-packet is added from a TCP connection buffer the ringis rotated so the next sub-packet the ring adds will come from adifferent TCP connection buffer. Each sub-packet can be up to 512 bytesin a particular example. If the connection buffer has less than 512bytes waiting, the data available is added to the TMP packet.

In step 607, when a full TMP packet (roughly 1.5 kB in a particularexample) is built, it is sent. This can have three or more sub packets,depending on their size. The TMP packet will also be sent when there isno more data ready.

TMP unit 405 (shown in FIG. 4) and TMP unit 505 (shown in FIG. 5)implement the TMP protocol that communicates packets between front-end201 and back-end 203. The protocol is rides on top of universal datagramprotocol (UDP) in that network devices that handle TMP packets treatthem as UDP packets. However, TMP packets differ from standard UDPpackets in that they have additional unique header data defining aunique set of messages, outlined below, to support the TMPfunctionality. Also, the manner in which TMP packets are transferredonto the physical communication channel, referred to as the protocolbehavior, differs significantly from TCP.

TMP packets have a header that contains packet control information. SomeTMP packets also carry extra information in a data or payload portion.The packet control information includes, for example:

-   -   A connection number (that identifies the connection to which it        belongs)    -   A checksum for data integrity    -   A set of flags (which may be used or remain unused) for a        variety of purposes    -   A message type identifier    -   The confirmed message type        The rest of the packet header contains information or data which        can differ between packets, depending on the message type.

A short list of messages that can be sent by the TMP protocol includes:data, acknowledgments, connection requests and replies, timesynchronization requests and replies, resent data, control messages, QoSmessages, status requests and replies, suspend messages, and alerts.Packet header content which is specific to the message type is asfollows.

-   -   Acknowledgment        -   The last sequential confirmed sequence message        -   The confirmed message sequence number    -   Time Synchronization Request        -   Requester time index.    -   Time Synchronization Reply        -   The time that the request was received.        -   The time that the reply was sent.        -   Requester time index.    -   Connection Request        -   The connections index (zero for a new connection).        -   Requested receiving port.        -   An additional set of flags (which may be used or unused) for            a variety of purposes.    -   Connection Reply        -   The replier's base time.        -   A time offset from the point of receiving the request in            milliseconds.        -   The connections index (zero for a new connection).        -   An additional set of flags (which may be used or unused) for            a variety of purposes.    -   Data        -   Data sequence number.        -   Time that the message was sent.

The rest of the packet comprises the packet body or payload portion.Alert and Acknowledge packets do not have bodies. All other packetscontain bodies that carry additional information appropriate to themessage itself (for example, a data packet will send the data itself).

It is important to note that alerts and QoS information are built intothe protocol and do not need to be passed as data packets. Since thesetypes of information are not built into TCP they would need to be sentas data, which might affect the application using the protocol. Thismeans that the receiving end needs to process the packet only once todraw out the information it requires. In contrast, when QoS informationis sent as a data packet in TCP, the receiving end has to process thepacket as a data packet simply to get to the information that allows thealert or QoS information to be processed, which means that TCP mustdouble the amount of processing for alerts and QoS information.

Of particular interest in the present invention, the exchange of timesynchronization information 707 enables front-end 201 and back-end 203to have a common time base and ascertain the time of issue of anyreceived packet. While the current implementation does not include basetime or time index data in the header of data packets, this informationcan readily be included in all message types, a subset of message types,and/or in a special message type defined for real-time data transport.In this manner, the recipient of a TMP packet knows with a high level ofcertainty when a received packet was transmitted, something thatexisting Internet protocols do not provide. In the case of TMP packetsfrom a back-end 203 to a front-end 201, the information can be used bythe front-end 201 as a factor in ordering responses to clients 205. Inthe case of TMP packets from a back-end 203 to a front-end 201, theinformation can be used by the front-end 203 as a factor in orderingresponses to clients 205.

Rather than synchronizing clocks the front-end 201 and back-end 203(i.e., absolute time synchronization), the time synchronizationinformation 707 may indicate a differential between the clocks of thetwo machines (i.e., relative time synchronization). Relative timesynchronization can be used substantially equivalently to informationthat would allow actual synchronization of the clocks. Accordingly,“time synchronization” and “time synchronized” refer inclusively to bothabsolute and relative time synchronization methods.

The time synchronization information 707 augments or replaces the “timeto live” feature of conventional IP packets. Each IP packet specifies atime to live value that must be decremented by each router or devicethat handles the packet. As the time value can only be incremented inone-second units, the value becomes a hop count rather than an actualtiming function. When a packet's time to live value is decremented tozero, it is discarded and must be retransmitted. In accordance with thepresent invention, the time to live value for TMP packets can be usedmore meaningfully as the recipient knows when the packet was actuallysent and can set or reset the time to live value to a meaningful valuewhen the packet leaves a front-end 201 or back-end 203.

As in all protocols, the messages in TMP have an order in which they aresent as well as particular defined situations in which they are sent. Atypical TMP session might begin with a connection request. Forreference, the end point that sends the connection request will bereferred to as the front-end, and the receiver of the request will bereferred to as the back-end, although the TMP protocol operatesbi-directionally between front-ends and back-ends. The front-end 201sends a connection request to the back-end 203, and the back-end 203sends a connection reply back to the front-end 201. This reply will beeither positive (connection accepted), or negative (connection refused).If the reply is positive, then the connection is established and thefront-end and back-end can begin to exchange data.

TMP is a TCP-like protocol adapted to improve performance for multipleconnections operating over a single pipe. The TMP mechanism inaccordance with the present invention creates and maintains a stableconnection between two processes for high-speed, reliable, adaptablecommunication. TMP is not merely a substitute for the standard TCPenvironment. TMP is designed to perform particularly well inheterogeneous network environments such as the Internet. TMP connectionsare made less often than TCP connections. Once a TMP connection is made,it remains up unless there is some kind of direct intervention by anadministrator or there is some form of connection-breaking networkerror. This reduces overhead associated with setting up, maintaining andtearing down connections normally associated with TCP.

Another feature of TMP is its ability to channel numerous TCPconnections through a single TMP pipe 202. The environment in which TMPresides allows multiple TCP connections to occur at one end of thesystem. These TCP connections are then mapped to a single TMPconnection. The TMP connection is then broken down at the other end ofthe TMP pipe 202 in order to traffic the TCP connections to theirappropriate destinations. TMP includes mechanisms to ensure that eachTMP connection gets enough of the available bandwidth to accommodate themultiple TCP connections that it is carrying.

Another advantage of TMP as compared to traditional protocols is theamount of information about the quality of the connection that a TMPconnection conveys from one end to the other of a TMP pipe 202. As oftenhappens in a network environment, each end has a great deal ofinformation about the characteristics of the connection in onedirection, but not the other. QoS information 708 is exchanged betweenfront-end 201 and back-end 203 in accordance with the present invention.By knowing about the connection as a whole, TMP can better takeadvantage of the available bandwidth.

A QoS message is sent alone or may be piggybacked on a data packet. Itsends information regarding the connection from one end of theconnection to the other. Both front-end 201 and back-end 203 send QoSmessages. The information in a QoS message is the most up to date thatthe sending end has. That means that if a QoS message is to be resent,the QoS information is updated before it is resent. A QoS message isidentified by the message type flag QoS. In a particular implementation,a QoS message contains:

-   -   16 Bits—Average round trip time (RTT). This indicates the        average round trip time as calculated by this end of the system        over the last time interval, measured in milliseconds.    -   32 Bits—Packets Sent. This indicates the number of packets that        were sent in the last time interval.    -   32 Bits—Packets Received. This indicates the number of packets        that were received in the last time interval.    -   32 Bits—Packets Resent. This indicates the number of packets        that needed to be resent in the last time interval.    -   16 Bits—Window Size. This value indicates the current window        size that one end is operating under. This will allow for a        random sampling of window sizes to be gathered at the other end.    -   16 Bits—Packets in Flight. This value indicates the current        number of packets that one end has sent to the other end without        receiving an acknowledgement. This will allow for a random        sampling of packets in flight to be gathered by the other end.    -   32 Bits—Time Interval. The span of time that the information in        the QOS packet is dealing with. This parameter is measured in        seconds.

In this manner, both front-end 201 and back-end 203 are aware of notonly their own QoS metrics, but also those of the machine with whichthey are communicating and their shared communication link.

As suggested in FIG. 7, QoS information 708 and time synchronizationinformation 707 can be used by blender 404 to select the order in whichdata is placed into TMP units 705. Also, QoS information 708 can be usedby TMP mechanisms 405 and 505 to alter the TMP behavior.

In contrast with conventional TCP mechanisms, the behavior implementedby TMP mechanism 405 is constantly changing. Because TMP obtainsbandwidth to host a variable number of TCP connections and because TMPis responsive to information about the variable status of the network,the behavior of TMP is preferably continuously variable. One of theprimary functions of TMP is being able to act as a conduit for multipleTCP connections. As such, a single TMP connection cannot behave in thesame manner as a single TCP connection. For example, imagine that a TMPconnection is carrying 100 TCP connections. At this time, it loses onepacket. TCP would require that the connection bandwidth be cut in half.This is a performance reduction on 100 connections instead of just onthe one that lost the packet.

Each TCP connection that is passed through the TMP connection must get afair share of the bandwidth, and should not be easily squeezed out bycompeting users of the available bandwidth. To allow this to happen,every TMP connection becomes more aggressive in claiming bandwidth as itaccelerates. Like TCP, the bandwidth available to a particular TMPconnection is measured by its window size (i.e., the number ofoutstanding TCP packets that have not yet been acknowledged). Bandwidthis increased by increasing the window size, and relinquished by reducingthe window size. Up to protocol specified limits, each time a packet issuccessfully delivered and acknowledged, the window size is increaseduntil the window size reaches a protocol specified maximum. When apacket is dropped (e.g., no acknowledge received or a resend packetresponse is received), the bandwidth is decreased by backing off thewindow size. TMP also ensures that it becomes more and more resistant tobacking off (as compared to TCP) with each new TCP connection that ithosts. Further, a TMP should not go down to a window size of less thanthe number of TCP connections that it is hosting.

In a particular implementation, every time a TCP connection is added to(or removed from) what is being passed through the TMP connection, theTMP connection behavior is altered. It is this adaptation that ensuressuccessful connections using TMP. Through the use of the adaptivealgorithms discussed above, TMP is able to adapt the amount of bandwidththat it uses. When a new TCP connection is added to the TMP connection,the TMP connection becomes more aggressive to accommodate it. When a TCPconnection is removed from the TMP connection, the TMP connectionbecomes less aggressive.

TMP connection 202 provides improved performance in its environment ascompared to conventional TCP channels, but it is recognized that TMP 202resides on the Internet in the preferred implementations. Hence, TMPmust live together with many protocols and share the pipe efficiently inorder to allow the other transport mechanisms fair access to the sharedcommunication bandwidth. Since TMP takes only the amount of bandwidththat is appropriate for the number of TCP connections that it is hosting(and since it monitors the connection and controls the number of packetsthat it puts on the line), TMP will exist cooperatively with TCPtraffic. Furthermore, since TMP does a better job at connectionmonitoring than TCP, TMP is better suited to throughput and bandwidthmanagement than TCP.

FIG. 8 illustrates an exemplary set of processes 808 implemented bypre-processing units 408 and 508. Some, none, or all processesillustrated in FIG. 8 may be implemented on particular packets asdescribed hereinbefore. Unprocessed payload 801 from a payload portionof a packet are passed to processes 808 that perform encryption,compression, and/or error correction. The actual algorithms used toimplement encryption, compression and/or error correction in anyspecific implementation are a design choice made be to meet the needs ofa particular application. Error correction is preferably forward errorcorrection that adds redundant data to the pre-processed payload so thata recipient can reconstruct the payload portion in the presence of oneor more transmission errors. The amount and format of redundantinformation can be varied dynamically to account for current QoSconditions as reported by, for example, QoS information 708.

FIG. 9 illustrates an exemplary set of processes implemented bypost-processing units 407 and 507. Some, none, or all processesillustrated in FIG. 9 may be implemented on particular packets dependingon the corresponding pre-processing performed on the packets.Pre-processed packets are passed to processes that perform decyrption,decompression, and/or error correction decoding. The actual algorithmsused in any specific implementation are determined to complement thepre-processing processes. Error correction operates to detect one ormore transmission errors, determine if the detected errors arecorrectable, and when correctable, reforming the corrected payload.Payload portion 903 is essentially a fully-formed payload portion of,for example, an HTTP packet.

Although the invention has been described and illustrated with a certaindegree of particularity, it is understood that the present disclosurehas been made only by way of example, and that numerous changes in thecombination and arrangement of parts can be resorted to by those skilledin the art without departing from the spirit and scope of the invention,as hereinafter claimed. For example, while devices supporting HTTP datatraffic are used in the examples, the HTTP devices may be replaced oraugmented to support other public and proprietary protocols andlanguages including FTP, NNTP, SMTP, SQL and the like. In suchimplementations the front-end 201 and/or back-end 203 are modified toimplement the desired protocol. Moreover, front-end 201 and back-end 203may support different protocols and languages such that the front-end201 supports, for example, HTTP traffic with a client and the back-endsupports a DBMS protocol such as SQL. Such implementations not onlyprovide the advantages of the present invention, but also enable aclient to access a rich set of network resources with minimal clientsoftware.

1. A data transport mechanism comprising: an interface for communicatingdata with a plurality of data transport links; a blender operable tomultiplex the data from the plurality of data transport links into ashared-bandwidth channel.
 2. The transport mechanism of claim 1 whereinthe plurality of data transport links comprise fixed-bandwidth links. 3.The transport mechanism of claim 1 wherein the plurality of datatransport links comprise a homogenous set of user-level protocols. 4.The transport mechanism of claim 1 wherein the plurality of datatransport links comprise a heterogeneous set of user-level protocols. 5.The transport mechanism of claim 1 wherein the plurality of datatransport links comprise a homogenous set of transport layer protocols.6. The transport mechanism of claim 1 wherein the plurality of datatransport links comprise a heterogeneous set of transport layerprotocols.
 7. The transport mechanism of claim 1 wherein the pluralityof data transport links comprise a homogenous set of physical layerprotocols.
 8. The transport mechanism of claim 1 wherein the pluralityof data transport links comprise a heterogeneous set of physical layerprotocols.
 9. The transport mechanism of claim 1 wherein the sharedbandwidth channel pools channel maintenance overhead over the pluralityof data transport links.
 10. The transport mechanism of claim 1 whereinthe shared bandwidth channel composes data packets by selecting datafrom the plurality of data transport links.
 11. The transport mechanismof claim 1, wherein the blender regulates a portion of the sharedbandwidth allocated to particular one of the plurality of data transportlinks by controlling the rate at which data from the particular link isplaced into the data packets during composition.
 12. The transportmechanism of claim 1 wherein the blender regulates a portion of theshared bandwidth allocated to particular one of the plurality of datatransport links by controlling the order at which data from theparticular link is placed into the data packets during composition. 13.A data transport mechanism comprising: an interface for communicatingdata with a plurality of data transport links; a blender operable tocombine the data from the plurality of data transport links into ashared-bandwidth channel; and means for applying rate control to theshared-bandwidth channel such that rate control is aggregated across allof the plurality of data transport links.
 14. The data transportmechanism of claim 13, wherein the plurality of data transport linkscomprise fixed-bandwidth links.
 15. The data transport mechanism ofclaim 13, wherein the shared bandwidth channel pools channel maintenanceoverhead over the plurality of data transport links.
 16. The datatransport mechanism of claim 13, wherein the shared bandwidth channelcomposes data packets by selecting data from the plurality of datatransport links.
 17. A data transport mechanism comprising: an interfacefor communicating data with a plurality of data transport links; and ablender operable to multiplex the data from the plurality of datatransport links into a shared-bandwidth channel, wherein the blenderregulates a portion of the shared bandwidth allocated to particular oneof the plurality of data transport links by controlling the rate atwhich data from the particular link is placed into the data packetsduring composition; and wherein the blender regulates a portion of theshared bandwidth allocated to particular one of the plurality of datatransport links by controlling the order at which data from theparticular link is placed into the data packets during composition. 18.The data transport mechanism of claim 17, wherein the plurality of datatransport links comprise fixed-bandwidth links.
 19. The data transportmechanism of claim 17, wherein the shared bandwidth channel poolschannel maintenance overhead over the plurality of data transport links.20. The data transport mechanism of claim 17, wherein the sharedbandwidth channel composes data packets by selecting data from theplurality of data transport links.